Stroke (apoplexy) involves sudden loss of neural function due to disturbance in cerebral perfusion owing to intracranial and extracranial angiemphraxis or angiorrhexis, which seriously harms the health of the aged and middle-aged as a main cause of disability and death. About one third of patients attacked by the disease will develop to death; even survivors will lose their work ability or self-care ability due to sequelae such as hemiplegia and aphasia. At present, there are two treatments available for stroke: One is to relieve deficiency of oxygen and glucose in arteries via increasing blood flow; the other is to protect neuron through blocking neuron death caused by cerebral ischemia and excitotoxicity. Clinically used neuron protective agents include calcium channel blockers, glutamate receptor antagonists and NMDA antagonists etc. However, in view of the high morbidity, mortality and disability rates, there are few drugs developed for prevention and treatment of stroke, which is far from enough to meet clinical need.
Rhizome Anemarrhenae as an herbal medicine, is rhizome of Anernarrhena asphodeloides Bge, anemarrhena of family Liliaceae, which is mainly produced in Hebei, Inner Mongolia, Shanxi and northeast China. In traditional Chinese medicine, it is used as a bitter cold heat-clearing drug with effects of relieving exogenous febricity, hyperpyrexia and polydipsia, lung-heat and dry cough, osteopyrexia and fevers calor intemus and diabetes and dryness of the intestine and constipation. Essential component of anemarrhenae is steroidal saponins. To date, 32 kinds of steroidal saponins and sapogenin isolated from anemarrhenae have been reported as well as other components such as chromocor, oligosaccharide, polysaccharides, fatty acid, etc. Kawasaki et al. first isolated the timosaponin BII in 1963, but did not elucidate its chemical structure. Seiji Nagumo et al. elucidated the chemical structure of timosaponin BII first in 1991 (Seiji NAGUMO et al, J. Pharm. (Japanese), 1991: 111(1); 306-310). From then on, extraction and activity determination of Timosaponin BII were reported by Noboru Nakashima (NOBORU NAKASHIMA et al, Journal of Natural Products, 1993; 56(3): 345-350), Ma Bai ping (Ma B P et al., Yao Xue Xue Bao, 1996: 31(4): 271-277), Masayasu Kimula (Masayasu KIMURA et al, Biol. Pharm. Bull, 1996; 19(7); 926-931), Jianying Zhang (Jianying ZHANG et al, Clinica Chimica Acta, 1999; 289: 79-88) successively.
Timosaponin BII, also called Prototimosaponin AIII, is the essential component of anemarrhenae. Its chemical name is (25S)-26-O-β-D-glucopyranosyl-22-hydroxy-5β-furostane-3β,26-diol-3-O-β-D-glucopyranosyl(1→2)-β-D-galactopyranoside, with structural formula shown as follow:

The pharmacological activities of Timosaponin BII that have been reported mainly include:    1. Hypoglycemic activity. Timosaponin BII can lower blood sugar level in streptozocin-induced diabetic mouse without promoting absorption of glucose and release of insulin. The mechanism of reducing blood glucose is supposed to be the inhibition of liver sugar decomposition (NOBORU NAKASHIMA et al, Journal of Natural Products, 1993; 56(3): 345-350)    2. Inhibition of platelet aggregation. Timosaponin BI possesses activity of obviously inhibiting platelet aggregation and prolonging clotting time (Jianying ZHANG et al, Clinica Chimica Acta, 1999; 289:79-88).    3. Clearance of free radicals. Observation via paramagnetic method shows that timosaponin BII can clear 57% free radicals generated from Fenton reaction system (Ma B P, et al. Yao Xue Xue Bao, 1996; 31(4): 271-277).    4. Anti-dementia activity. Ma Bai ping et al. reported that timosaponin BII have preventive and therapeutic effect against senile dementia (Chinese Patent Application Publication No. CN1212966, Application No. 97119680.X).
Chen Wan sheng et al. reported the use of total Timosaponins in preparation of medicaments for prevention and treatment of stroke (Chinese Patent Application Publication No. CN1451384A Application No. 03116824.8). The total timosaponins disclosed therein are characterized by a sum of contents of timosaponins BII, E, B, AIII of ≧50%.